i have an '89 S2 also, and love it. i just put it away for the new york winter, and unfortunately, storage always has some ill effects on any car, more so an almost 20 yr old example. There are definitely things you can and should do, but storage tends to dry out rubber parts; seals, bushings, o-rings, boots etc., so it might help to spray some of the accessible parts with a protectant-sealant. Everything recommended here by others sounds good, but probably more important is what you do when you take the vehicle out of storage. There is no drain plug for the gas tank but if you consider changing the filter, you may be able to remove it and let the pump push the gas out for you (i don't know for sure if this would work, i've never tried it) and then install the new one.
Here is a sure sign it's time to put your baby away for a long winter nap:
